Process for preparing antimicrobial microcapsules

Abstract

More particularly, the present invention relates to a process for producing antimicrobial core-shell microcapsules with immobilized silver particles into and onto the shell. The latter can be used in home or personal care products for delivering a perfuming and malodor-countering effect. The microcapsules obtainable by such a process and the consumer products comprising these microcapsules are also objects of the invention.

What is claimed is: 
     
       1. A process for the preparation of antimicrobial polyurea-based core-shell microcapsules comprising the following steps:
 a) dissolving at least one polyisocyanate in an active ingredient to form an oil phase; 
 b) dispersing the oil phase into an aqueous solution comprising an anionic emulsifier to form an oil-in-water emulsion; 
 c) adding to the oil-in-water emulsion a polyamine, a silver salt and a reducing agent provided that the reducing agent is added after the silver salt; to form a slurry of microcapsules having polyurea-based walls comprising silver particles in or on the walls; and 
 d) obtaining the microcapsules from the slurry. 
 
     
     
       2. The process according to  claim 1 , wherein the silver salt is selected from the group consisting of silver nitrate, silver citrate, silver chloride, silver iodide, silver sulphate and silver bromide. 
     
     
       3. The process according to  claim 1  wherein the reducing agent is selected from the group consisting of sodium borohydride, mono and disaccharide, sodium citrate, ascorbic acid, formic acid, oxalic acid, hydrazine, lithium aluminium hydride, and ascorbate. 
     
     
       4. The process according to  claim 1  wherein the silver salt is used in an amount comprised between 0.01 and 10% by weight, relative to the total weight of the microcapsules slurry. 
     
     
       5. The process according to  claim 1  wherein the silver salt and the reducing agent are used in a weight ratio comprised between 1:1 and 5:1. 
     
     
       6. The process according to  claim 1  wherein at least one polyisocyanate is selected from the group consisting of a polyisocyanurate of toluene diisocyanate, a trimethylol propane-adduct of toluene diisocyanate, a trimethylol propane-adduct of xylylene diisocyanate, a trimer of hexamethylene diisocyanate, a trimer of isophorone diisocyanate, a trimethylol propane-adduct of hexamethylene diisocyanate, a biuret of hexamethylene diisocyanate and mixtures thereof. 
     
     
       7. The process according to  claim 1  wherein at least one polyisocyanate is used in an amount comprised between 2 and 30% by weight, relative to the total weight of the oil phase. 
     
     
       8. The process according to  claim 1  wherein the anionic emulsifier is selected from the group consisting of acylglycinate salts, polyvinyl alcohol, cellulose polymers, sodium dodecyl sulfate, polyvinyl pyrrolidone, anionic polyelectrolytes, bovine serum albumin and gum arabic. 
     
     
       9. The process according to  claim 1  wherein the polyamine is selected from the group consisting of 1,2-diaminopropane, 1,2-diaminoethane, diethylenetriamine, water soluble guanidine salts, guanidine, tris-(2-aminoethyl)amine, N,N′-bis(3-aminopropyl)-ethylenediamine, N,N,N′,N′-tetrakis(3-aminopropyl)-1,4-butanediamine and 3,5-diamino-1,2,4-triazole. 
     
     
       10. The process according to  claim 1  wherein the active ingredient is a perfume with a concentration comprised between 20 and 50% by weight relative to the total weight of the microcapsules slurry. 
     
     
       11. The process according to  claim 1  wherein the microcapsules obtained comprise between 100 and 10000 ppm of silver particles. 
     
     
       12. Antimicrobial core-shell polyurea-based microcapsules obtainable by process as defined in  claim 1 , said microcapsules comprising:
 a polyurea-based wall, which comprises the reaction product of the polymerization between at least one polyisocyanate and at least one polyamine; 
 a silver particle on or in the polyurea-based wall; 
 an anionic emulsifier; and 
 an encapsulated active ingredient; 
 wherein the silver particles are generated during the interfacial polymerisation. 
 
     
     
       13. The antimicrobial polyurea-based microcapsules according to  claim 12 , characterized in that the size of silver particles is between 5 and 500 nm. 
     
     
       14. A perfuming composition comprising
 a) as perfuming ingredient, microcapsules according to  claim 12 ; 
 b) at least one ingredient selected from the group consisting of a perfumery carrier and a perfumery co-ingredient. 
 
     
     
       15. A perfuming consumer product comprising as a perfuming ingredient, a perfuming composition according to  claim 14 . 
     
     
       16. A perfuming consumer product according to  claim 15 , in the form of a deodorant or antiperspirant, a fabric or air refresher, a hard surface cleanser and deodorizer, a non-woven fabric and a cat litter. 
     
     
       17. A perfuming composition comprising
 c) as perfuming ingredient, microcapsules according to  claim 13 ; 
 d) at least one ingredient selected from the group consisting of a perfumery carrier and a perfumery co-ingredient. 
 
     
     
       18. A perfuming consumer product comprising as a perfuming ingredient a perfuming composition according to  claim 17 . 
     
     
       19. A process for the preparation of antimicrobial polyurea-based core-shell microcapsules comprising the following steps:
 a) dissolving at least one polyisocyanate in a perfume to form an oil phase; 
 b) forming an oil-in-water emulsion by dispersing the oil phase into an aqueous solution comprising an anionic emulsifier; 
 c) adding to the oil-in-water emulsion a polyamine, a silver salt and a reducing agent with the reducing agent added after the silver salt to form microcapsules with polyurea-based walls comprising silver particles in and on the walls. 
 
     
     
       20. Antimicrobial core-shell polyurea-based microcapsules obtainable by process as defined in  claim 19 , said microcapsules comprising:
 a polyurea-based wall, which comprises the reaction product of the polymerization between at least one polyisocyanate and at least one polyamine; 
 a silver particle on and in the polyurea-based wall; 
 an anionic emulsifier; and 
 an encapsulated perfume; 
 wherein the silver particles are generated during the interfacial polymerisation.